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Old 21st November 2013, 11:25 AM   #1
Eldam is offline Eldam  France
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Join Date: Sep 2012
Default ARTA & sweep sine : which protocol ?

Hi,

I hope to measure my speaker but I can't. Just want to see big default : > + 3 db peak after 2 khz.

I use ARTA, Tracker Pre usb soundcard checked by ARTA, EMC-8000 mic without calib file. ASIO Creative driver and the USB2 out of my Windows XP Laptop.

I was advised to use sweep sine with peak hold to low the problems of room with simple Pink noise measurement. I use the sweep sine wave of audiocheck web site.

Is there a protocol or can i be advised for the setting up of ARTA :

Windows: Uniform, Hanning, flat top ?
Averaging : peak hold : I suppose
Smoothing function : on ?
Frequency & FFT : ?

Which set up for the windows graph : 100 DB with 40 DB to have 5 DB from line to line ?

Is there somebody who can show me a typical SPA curve without measurement (before Rec) because mine is very very non flat... and I d'ont understand if it's the noise or a normal thing at - xx DB (no sound). How much DB amplitude between the 2 curves: silence and with generated noise ?

Whith a pink noise or a sweep sine (are they non periodic noise ?) how much DB levelfor a correct measurement : 60 DB ?

Sorry if basics questions but need help please, i found many papers about measurement but none for beginners with ARTA and none showing the right set up to expect trusted measurement. Maybe my bad, not efficient with googling in english .
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Old 30th December 2013, 01:20 PM   #2
cedus is offline cedus  France
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Several ARTA tutorials (in French) on different uses and made by nice people :
MELAUDIA :: forums - mesures
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Old 30th December 2013, 01:46 PM   #3
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System setup is checked with loopback measurement from pre out connected to input. Sweep from <10Hz to 1/2 sampling rate (24kHz for fs48kHz).

Result should be super flat above 10Hz.

Common problem is having some manner of monitor mixing that is mixing input signal back onto output signal.

Windowing choices are based on measurement conditions. With IR returned by swept sine process, import point is capturing entire IR.

For speaker measurements, windowing and gating are used to limit room reflections influence, but also limits LF resolution of measurement result.
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Old 30th December 2013, 02:53 PM   #4
Eldam is offline Eldam  France
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Join Date: Sep 2012
thanks Cedus & Barelywater for the inputs.

I will check again the post of Melaudia web site (jmlc did learning campus at Rueil Malmaison...) but if I remember it is the classical method with wires to send noise generated by Arta. Like too the "How to" of CharlieLaub Diya's fellow.

I seted up the software with the loopback wire on the EMU tracker pre USB sound card but use after external noise noise wave files for measurement (easy cause i use music server with tuned logitech SB duet streamer + DAC) with remote control.

I use diffferent wave record : swept sine and pink noise : so without wires to the main pre of the hifi system... Somebody told me it does not give acurate result and used RTA instead... which gave me the same results

It seems that I have to buy wires between Pre sound card and preamplifier for using time windows method ! Because Arta has been developed for the use of its own injected noise files !

In RTA there is az function to flat the curve of the mic before recording
In Arta, there is "only" the mic file correction. I made my self mic file correction to have a flat curve before recording above 1000 hz. But don't know if it's a valid solution, i found logical to minimize the sound signature of the mic and the room in a very silent environement (midle of the night) by making the curve flat with hand correction in the mic file... By the way the curve change with the windows (Hannoning, normal, etc).

Barelywater, my understanding with your input is that I must have a flat curve when ARTA is switched on in a silent room and with a relative good enough mic like my Behringer ECM8000 (with non calibrate file) ?
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Old 30th December 2013, 10:31 PM   #5
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You must have flat response of measurement system first.

Microphone needs reference against know microphone.
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Old 30th December 2013, 10:52 PM   #6
Eldam is offline Eldam  France
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Thanks,

I understand the flatering curve function before recording in the True RTA software now.

By the way find ARTA windows more pleasant. Just can't understand why it doesn't exist in ARTA?

Is a mic calib file very usefull if having no anechoic chamber ? Does the flatering option in True ARTA have the same acuracy than a mic calib file ? Same job ?
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Old 31st December 2013, 12:03 AM   #7
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Without referencing microphone to known standard, results for use in adjusting unknown speaker are of little use.

Here is overlay plot from many ECM8000 microphones from a calibration service:

Click the image to open in full size.

All the above plots are normalized to 0dB at 1kHz. Actual microphone sensitivities between units varies as well.

ECM8000 without calibration data is of little use.
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Old 31st December 2013, 01:59 PM   #8
Eldam is offline Eldam  France
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Join Date: Sep 2012
thank you Barelywater,

i will buy a new mic with calib file and wires to use Arta with Time Window. Some said to me it was flat enough for current works without calib file in domestic room but if we have to, let's go !

Duce,

Thank you, I have been seeing the threads at Melaudia from yesterday but nothing written about the beginning of the set up before measuring... (how have to be the curve before recording). Ok barely said it has to be flat but mine is like the Mont Blanc ! with or without generic calib file for my ECM8000. Saw too the great work of JMLC to explain CSD and polar response measurement with ARTA. He leaved us... sad news.

Last edited by Eldam; 31st December 2013 at 02:01 PM.
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